A Keen Crow

Love this mod. Just a question regarding the special zombies, though. My friend and I have encountered numerous spider zombies (jumpers) and cops, but they don't seem to behave as they do in the vanilla version. This is to say, the spiders don't jump and the cops don't spit or explode. Is this intended or have we just been "lucky"? We're currently at day 25 with a game stage of about 110 each (if I recall correctly).